CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container, www.caribic-atmospheric.com) deploys a large suite of instruments for atmospheric measurements onboard a Lufthansa Airbus A340-600 on a monthly basis. The regular flights included several roundtrips between Germany and Japan in 2009 and 2010 into regions strongly influenced by Asian outflow.

In May 2009 and June 2010 exceptionally high mixing ratios of carbon monoxide with a maximum value of 764 ppb were measured in the upper troposphere over Korea and the Sea of Japan. At altitudes above 8 km, four individual plumes were encountered, three of these in the vicinity of a tropopause fold in air masses that were characterized by stratospheric indicators such as high potential vorticity. In addition to measurements of CO, complementary equipment allows for a detailed characterization of air masses. Measurements of nitrogen oxides and aerosol particles indicate that the polluted air masses had already been processed to some degree. Correlations of CO with trace gases not associated with biomass burning, such as SF6, indicate that the pollution plumes had a strong industrial/anthropogenic component. Trajectory calculations point to continental Asia as possible regions of origin. The events are considered rare occasions of the combination of anthropogenic emissions and wildfires.